Detection of uneven hoisting of a Tainter lock gate: a case study for The Dalles Lock and Dam

The upstream lock gate at The Dalles Lock and Dam on the Columbia River is a radial, or Tainter, gate. Tainter gates operate by being raised and lowered through a circular path by means of hoisting cables. The continued operability of the gate is of extreme economic importance to the Columbia River basin region, as the gates facilitate the transportation of billions of dollars in goods annually. One of the critical issues during operation of the gate is uneven, or skewed, hoisting of the gate, which causes twisting in the gate leading to the potential for unaccounted stresses. This study focuses on the operational behavior of the Tainter gate at The Dalles and detection of uneven hoisting during gate operation. The initial goal of this study was to develop an automated method to detect uneven hoisting of the gate utilizing strain gage data from a continuous monitoring system. However, disagreement between the incoming data compared to the expected behavior of the gate led to concerns about the Tainter gate. Three explanations for the disagreement seemed possible: the model of the gate was flawed, the sensors were unreliable, or the gate was actually already hoisting unevenly. To provide a definitive diagnosis of the issues seen in the data, a short-term monitoring program was devised using vibration measurements of the hoisting cables of the gate. Then, a frequency domain method was employed to estimate the force in the cables, which provides an indication of the unevenness of the gate hoisting. Results indicate that, indeed, the Tainter gate at The Dalles regularly hoists unevenly and that the installed sensor system is sensitive to the presence of uneven hoisting.